This invention relates in general to cushioning devices and, more particularly, to a wheelchair cushion which features an orthotic base which shapes on contact to wraparound the buttocks of the user, i.e., the person seated on the base, to immerse the user in the base and increase surface area contact between the user and the base, thereby reducing the peak pressures on the skin surface of the user. The invention also accommodates air cell and/or soft foam additions to the surface of the orthotic base which will further enhance fitting the shape of the person on contact so as to enhance wraparound of the buttocks of the user to, in effect, immerse the person and increase surface area contact between the user and the cushion. The orthotic wraparound base is designed to have a combination of support pillars of various lengths and an interconnecting top layer, both of which can be molded of one material in a flat mold, or alternatively assembled from individual parts. In this alternative assembly, cut pieces of foam or plastic equivalent to the pillars are attached with glue or mechanical fasteners to the under side of a flexible sheet of plastic or a sheet of foam.
Those who must spend extended time in wheelchairs run the risk of tissue breakdown and the development of ischemic sores, which are extremely dangerous and difficult to cure. These ischemic ulcers (pressure sores or decubitus ulcers), typically form in areas where bony prominences exist, such as the ischia, heels, elbows, ears and shoulders. Typically, when sitting, much of the individual's weight concentrates in the regions of the ischia, that is at the bony prominences of the buttocks, and unless frequent movement occurs, or there is a reduction in the deformation of these soft tissues, the flow of blood to the soft tissue in these regions decreases to the point that in time the tissue breaks down (this is known as necrosis). This problem is well known and many forms of cushions are especially designed for wheelchairs for reducing the concentration of weight in the region of the ischia, and these cushions generally seek to distribute the user's weight more uniformly over a larger area of the buttocks to reduce the amount of deformation to the soft tissues which include the vascular bed.
The trochanter area is another area where problems occur in wheelchair patients. To address this problem the bases for wheelchair cushions are shaped to try to load the thighs and reduce the suspension forces on the ischia and the trochanters. This distribution of suspension forces to the thighs serves as a fulcrum so the weight of the legs lifts the buttocks. Still another problem with wheelchair type cushions is stabilization and positioning of the user, so that he has a feeling of security and improved functionability when sitting in the wheelchair. To address this, the fulcrum point needs to be movable and the fit of the cushion to be adjustable to suit the individual, thereby attaining the optimum balance of suspension forces in each individual user.
A number of patents issued to Robert H. Graebe show cellular cushions which comprise an array of closely spaced cells which project upwardly from a common base and are interconnected to permit an enclosed fluid, such as air, to transfer throughout the cushion. These cushions combine the most uniform distribution of weight available in wheelchair cushions, and thus provide the greatest protection from the occurrence of ischemic ulcers/pressure sores. Since the cells communicate with each other in the Graebe cushions, all exist at the same internal pressure and each cell exerts essentially the same restoring force against the buttocks, irrespective of the extent to which it is deflected. Graebe U.S. Pat. No. 4,541,136 is typical of these patents and shows a cellular cushion currently manufactured and sold by Roho Inc. of Belleville, Ill. under license from Graebe for use on wheelchairs.
The stability problem has been attacked by the use of preshaped bases such as shown in Graebe U.S. Pat. No. 4,953,913 and Jay et al. U.S. Pat. No. 4,726,624. These bases are generally used in conjunction with cushions and Graebe U.S. Pat. No. 4,953,913 has been used in conjunction with a cellular cushion and a fabric cover. The stability problem also has been addressed in the cellular cushion field by the use of zoned areas of inflation as shown in Graebe U.S. Pat. Nos. 4,698,864 and 5,052,068 which show zoned cellular cushions with cells of varying height and Graebe U.S. Pat. Nos. 5,163,196 and 5,502,855 which show other forms of zoned cushions with cells of uniform heights.
As noted, it is known to use rigid shaped bases in combination with a wheelchair user engaging cushion as shown in Jay et al. U.S. Pat. No. 4,726,624. It also is known to use an air cell cushion with a rigid shaped base as exemplified in the Roho TRI-MAX cushion. Graebe U.S. Pat. No. 5,369,828 shows another form of composite cushion which utilizes a rigid shaped foam base with a cellular pad on a flat rear surface with a fabric cover over the entire cushion.
Finally, Sias et al U.S. Pat. Nos. 4,605,582, 4.673,605 and D294,212 (now owned by Robert H. Graebe), also show a form of base with pillars and bubbles extending from both sides of a center member to support a user above a fixed surface.
The present invention comprises in its broadest sense a semi-rigid orthotic base having an adjustable support profile (attained by trimming individual support pillars) which is designed to conform to the general shape of a typical user's buttocks, and which can be reshaped to provide the desired positioning of the buttocks of the user. In addition to conforming to the user's buttocks, the base of this invention also has sufficient strength to support the weight of the user. The base has a series of spaced support pillars and a flexible interconnecting top layer. Using this invention, the support members on the underside of the base can be trimmed to provide, under load, a desired upper surface profile designed for and specifically adapted to the shape of the user. The elasticity and resilience of the base is such that when the load on the top is reduced or removed, the top surface of the base will recover to its original flat shape. This inherent characteristic helps the user to transfer on and off the cushion.
In another form of the invention, an optional air cell pad is positioned on the top layer of the base beneath the ischia of the user to equalize the suspension forces and to better assume the shape of the hips and its ischia, thereby reducing deformation of the vascular system and thus facilitating blood flow to the skin at these critical areas. A soft foam pad covers the remainder of the base, but has a cutout area to expose the air cells when they are used. This arrangement provides a continuous comfortable smooth feel for the user of the cushion over its entire surface area, while maintaining the therapeutic value of the air cells over the critical ischia area.
A foam balance pad with holes to match the base pillars can be positioned beneath the orthotic base to act as a fulcrum to tilt the base forward or backward or from one side to the other, depending on the balancing and positioning needs of the user. The foam pad is of lesser front to back size than the orthotic base. The balance pad can be inserted beneath and fitted into the pillars of the orthotic base and moved toward the front or rear of the base to correspondingly adjust the tilt of the base and the tilt of the user of the cushion. It can also be rotated beneath the base and moved from side to side to accommodate the postural needs of the user toward one side of the base or the other.
The present invention also provides for the use of a removable or fixed pommel at the center of the front of the base to divide the legs of the user. Removable side adjustment members also are positionable at the front and rear side edges of the base to further direct and locate the legs and buttocks of the user.
Removable shaped blocks can be positioned beneath the base and engaged with the pillars to similarly shape the base. The blocks can be of dense foam or wood and can be positioned at the center of the front of the base to form a pommel or beneath the side edges to bend the edges upwardly to induce positional and additional shape functions.